Intramyocardial Troponin-T Monitoring with Microdialysis in Coronary Artery Bypass Surgery

OBJECTIVE: To investigate the time course of troponin-T release into the extracellular fluid of the myocardium and to distinguish between a rise in troponin-T due to implantation trauma and an increase due to cardiac arrest during coronary surgery. DESIGN: Microdialysis probes were implanted in the heart of seven patients soon after sternotomy. Troponin-T was measured in the microdialysates and in peripheral blood from 3 h before to 24 h after heart arrest. RESULTS: The troponin-T concentration in the microdialysates increased immediately after probe implantation and decreased to baseline within 70 min. This early peak is interpreted to reflect a local trauma. Three hours after cross-clamp release, a second peak of microdialysate troponin-T was recorded; 50 times higher than in serum. Eight to 24 h later a third peak occurred in five patients. Serum troponin-T was below the detection level at the beginning of the operation but increased linearly during the first 3 h of reperfusion and remained at that level thereafter. CONCLUSION: Microdialysis is a safe technique providing more information on myocardial metabolism during and after bypass surgery than can be obtained from peripheral blood. The release of troponin-T in response to cardiac arrest can be distinguished in time from the local tissue response to probe implantation.